Doctor of Philosophy, The Ohio State University, 2011, Materials Science and Engineering

Recently, phase field computational models have been developed as tools for the investigation of microstructure formation at length scales, time scales, and levels of detail which would otherwise be unaccessible. These robust simulation techniques have been applied to study a wide variety of problems. This work details their application to the study of surface roughening and irradiation hardening. First, motivated by recently reported experimental observations, the role of coupling between elasticity, composition and structure during island formation in thin films will be examined. Localized stress centers (such as those caused by morphological or chemical variations in a film) and their influence on the formation of surface islands by the Asaro-Tiller-Grinfeld instability is investigated via the phase field method. Such stress centers are found to cause a wave-like marching of surface islands away from the centers during their formation, and these results are compared to experimental observation. Coupling between composition and stress is then introduced, and its influence on surface evolution and morphology is studied. Secondly, a phase field model of dislocations is employed to examine irradiation hardening in Zirconium. After neutron irradiation Zr-alloys develop a characteristic damage microstructure: populations of dislocation loops with -type Burgers vectors, believed to be formed by the condensation of point defects. These defect populations have been correlated with significant hardening in Zr-alloys, while the specific causal mechanism remains unknown. The phase field method is employed in order to study the specifics of damage loop and glide dislocation interaction at the mesoscale. Long-range elastic interactions are considered via the phase-field microelasticity theory, and an ad hoc methodology is developed to consider contact interactions. Dislocation glide is simulated in the presence of a representative population of damage loops, and the effect o (open full item for complete abstract)

Committee: Yunzhi Wang PhD (Advisor); Suliman A. Dregia PhD (Committee Member); Michael Mills PhD (Committee Member) Subjects: Materials Science